title: The effect of valproate (VPA) treatment on inositol phosphates (IPs) accumulation in non-stimulated and GnRH-treated female rat anterior pituitary cells in vitro.
abstract: OBJECTIVE
  Mechanism(s) responsible for VPA-induced effects on reproductive axis activity are not fully recognized. Previously we reported that VPA suppressed only GnRH-stimulated but not the basal LH release from rat anterior pituitary (AP) cells in vitro. Since the inhibitory effect of VPA was exerted only in GnRH-activated cells, potential VPA impact on GnRH-R-coupled IP3/PKC signaling could not be excluded. In this study the effect of VPA on IPs synthesis in non-stimulated and GnRH-treated rat AP cells was examined.
  
  
  METHODS
  In the first experiment 5 × 105 cells/ml were incubated for 3h with VPA (10 nM-10 μM), PMA (100 nM), GnRH (100 nM), PMA (100 nM) + VPA (10 nM-10 μM), GnRH (100 nM) + VPA (10 nM-10 μM). In the second experiment cells were preincubated for 24h with 1μCi myo-[23 H]-inositol, then for 30 min with 10 mM LiCl and finally for 3hr with GnRH (100 nM) VPA (1 μM, 10 μM), GnRH (100 nM) + VPA (1 μM, 10 μM). LH concentration was measured by RIA and intracellular IPs accumulation by ion-exchange chromatography analysis.
  
  
  RESULTS
  VPA diminished GnRH-stimulated LH release without affecting PMA-induced LH release at any dose tested. Moreover, VPA-induced increase of IPs accumulation occurred in both non-stimulated and GnRH-treated cells and intensity of cellular response was similar in both groups.
  
  
  CONCLUSIONS
  VPA affects IP3/PKC pathway activity through its up-regulatory effect on IPs synthesis in AP cells. VPA-induced inhibition of GnRH-stimulated LH release from gonadotrope cells appears to be the result of still unrecognized cellular mechanism.
authors.affiliation: Neuroendocrinology Department, The Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland. zncmkp@op.pl
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Wasilewska-Dziubinska
authors.forename: Alina
authors.initials: A
authors.lastname: Gajewska
authors.forename: Anna
authors.initials: A
authors.lastname: Herman
authors.forename: Ewa
authors.initials: E
authors.lastname: Wolinska-Witort
authors.forename: Justyna
authors.initials: J
authors.lastname: Skrzypska
authors.forename: Lidia
authors.initials: L
authors.lastname: Martynska
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Kalisz
authors.forename: Magdalena
authors.initials: M
authors.lastname: Chmielowska
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002852:Chromatography, Ion Exchange; D005260:Female; D018682:GABA Agents / Q000494:pharmacology*; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D007986:Luteinizing Hormone / Q000187:drug effects / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D018682:GABA Agents; D007987:Gonadotropin-Releasing Hormone; D014635:Valproic Acid; D015544:Inositol 1,4,5-Trisphosphate; D007986:Luteinizing Hormone; D011493:Protein Kinase C